'The dwarves' establishment of a foothold in Durin's halls could not have come at a more fortuitous time, for I find that the presence of a certain guest in our lands has drawn the eyes of many foes, near and far.
'There is a great presence of trolls in Dâr Narbugud, and they are deadly foes even when running carelessly about. Imagine the damage that could be done to the dwarves when the trolls are guided by leaders.
'The dwarves are doughty fighters, but I do not believe they will withstand the might of well-led trolls, least of all trolls corrupted by the sickness and plague brewing in Dâr Narbugud. You should destroy the leaders outright, and the lesser trolls will surely be weakened without proper guidance from their superiors. This task will require a great force, to be sure.'
The Elves believe that trolls give a great advantage to the enemy in battle, due to their massive strength and hardiness. The troll-leaders in Dâr Narbugud must be eliminated in order to weaken the enemy's forces.
The trolls you seek can be found in Dâr Narbugud, near the Dark Delvings at the southernmost tip of the Foundations of Stone.
Donfuin has asked you to defeat the trolls' leaders, which should disorganize the trolls and deflate their usefulness in battle.